Control circuits for power supplies are frequently embodied in integrated circuit form. Integrated circuits have an advantage of low cost when produced at high volume and, furthermore, have the advantage of high reliability as compared with circuits of similar type design utilizing discrete components. To achieve these benefits of integrated circuits design, an integrated control circuit must be versatile enough to permit wide application to varying sizes of power conditioning circuits.
Comparator type switching circuits are widely used in power supply control circuits. In switching regulator type power conditioning circuits, comparator type switching circuit is used to control the duty cycle of the switching device. It operates by comparing an error signal with a reference signal to determine the duty cycle of the switching device necessary to achieve a desired regulated output signal. Large current handling capacity and high switching speeds are desirable characteristics of an integrated comparator type switching circuit. These two desirable features, however, are antithetical operating characteristics. The handling of high currents in the output stages of the typical prior art comparator type switching circuit generates large storage charges in the semiconductor junctions which limit the switching speed.